WIP: Support binding by interpolation

This adds support for quoting/binding values to statements by
interpolation.

    db.prepare("SELECT * FROM users WHERE admin = \(true)" as quoted)
    // SELECT * FROM users WHERE admin = 1

Signed-off-by: Stephen Celis <stephen@stephencelis.com>

Author: stephencelis

SQLite Tests/DatabaseTests.swift

@@ -51,6 +51,7 @@ class DatabaseTests: SQLiteTestCase {
         db.prepare("SELECT * FROM users WHERE admin = ?", 0)
         db.prepare("SELECT * FROM users WHERE admin = ?", [0])
         db.prepare("SELECT * FROM users WHERE admin = $admin", ["$admin": 0])
+        db.prepare("SELECT * FROM users WHERE admin = \(false)" as quoted)
         // no-op assert-nothing-asserted
     }
 
@@ -59,15 +60,21 @@ class DatabaseTests: SQLiteTestCase {
         db.run("SELECT * FROM users WHERE admin = ?", 0)
         db.run("SELECT * FROM users WHERE admin = ?", [0])
         db.run("SELECT * FROM users WHERE admin = $admin", ["$admin": 0])
-        AssertSQL("SELECT * FROM users WHERE admin = 0", 4)
+        db.run("SELECT * FROM users WHERE admin = \(false)" as quoted)
+        AssertSQL("SELECT * FROM users WHERE admin = 0", 5)
+
+        var age: Int?
+        db.run("SELECT * FROM users WHERE age IS \(age)" as quoted)
+        AssertSQL("SELECT * FROM users WHERE age IS NULL")
     }
 
     func test_scalar_preparesRunsAndReturnsScalarValues() {
         XCTAssertEqual(0, db.scalar("SELECT count(*) FROM users WHERE admin = 0") as! Int64)
         XCTAssertEqual(0, db.scalar("SELECT count(*) FROM users WHERE admin = ?", 0) as! Int64)
         XCTAssertEqual(0, db.scalar("SELECT count(*) FROM users WHERE admin = ?", [0]) as! Int64)
         XCTAssertEqual(0, db.scalar("SELECT count(*) FROM users WHERE admin = $admin", ["$admin": 0]) as! Int64)
-        AssertSQL("SELECT count(*) FROM users WHERE admin = 0", 4)
+        XCTAssertEqual(0, db.scalar("SELECT count(*) FROM users WHERE admin = \(false)" as quoted) as! Int64)
+        AssertSQL("SELECT count(*) FROM users WHERE admin = 0", 5)
     }
 
     func test_transaction_executesBeginDeferred() {

SQLite/Database.swift

@@ -115,6 +115,15 @@ public final class Database {
         return prepare(statement).bind(bindings)
     }
 
+    /// Prepares a single SQL statement and binds parameters to it.
+    ///
+    /// :param: statement A SQL string interpolated with quoted values.
+    ///
+    /// :returns: The statement.
+    public func prepare(statement: quoted) -> Statement {
+        return prepare(statement.SQL).bind(statement.bindings)
+    }
+
     // MARK: - Run
 
     /// Runs a single SQL statement (with optional parameter bindings).
@@ -151,6 +160,15 @@ public final class Database {
         return prepare(statement).run(bindings)
     }
 
+    /// Prepares, binds, and runs a single SQL statement.
+    ///
+    /// :param: statement A SQL string interpolated with quoted values.
+    ///
+    /// :returns: The statement.
+    public func run(statement: quoted) -> Statement {
+        return prepare(statement.SQL).run(statement.bindings)
+    }
+
     // MARK: - Scalar
 
     /// Runs a single SQL statement (with optional parameter bindings),
@@ -190,6 +208,16 @@ public final class Database {
         return prepare(statement).scalar(bindings)
     }
 
+    /// Prepares, binds, and runs a single SQL statement, returning the first
+    /// value of the first row.
+    ///
+    /// :param: statement A SQL string interpolated with quoted values.
+    ///
+    /// :returns: The first value of the first row returned.
+    public func scalar(statement: quoted) -> Binding? {
+        return prepare(statement.SQL).scalar(statement.bindings)
+    }
+
     // MARK: - Transactions
 
     /// The mode in which a transaction acquires a lock.

SQLite/Statement.swift

@@ -230,6 +230,54 @@ extension Statement: Printable {
 
 }
 
+extension Statement {
+
+    public struct Interpolation {
+
+        internal let SQL: String
+
+        internal let bindings: [Binding?]
+
+        private init(literal SQL: String = "", _ bindings: [Binding?] = []) {
+            (self.SQL, self.bindings) = (SQL, bindings)
+        }
+
+    }
+
+}
+
+// MARK: - StringInterpolationConvertible
+extension Statement.Interpolation: StringInterpolationConvertible {
+
+    public init(stringInterpolation components: Statement.Interpolation...) {
+        var (SQL, bindings) = ("", [Binding?]())
+        for (idx, component) in enumerate(components) {
+            if idx % 2 == 0 {
+                SQL += component.bindings.first as! String
+            } else {
+                SQL += component.SQL
+                bindings.extend(component.bindings)
+            }
+        }
+        self.init(literal: SQL, bindings)
+    }
+
+    public init<T: Value>(stringInterpolationSegment value: T) {
+        self.init(literal: "?", [value.datatypeValue])
+    }
+
+    public init<T: Value>(stringInterpolationSegment value: T?) {
+        self.init(literal: "?", [value?.datatypeValue])
+    }
+
+    public init<T>(stringInterpolationSegment expr: T) {
+        self.init(literal: "?", [toString(expr)])
+    }
+
+}
+
+public typealias quoted = Statement.Interpolation
+
 public func && (lhs: Statement, @autoclosure rhs: () -> Statement) -> Statement {
     if lhs.status == SQLITE_OK { lhs.run() }
     return lhs.failed ? lhs : rhs()